(See also Overview of the Cranial Nerves.)
Hemifacial spasm is painless involuntary twitching of one side of the face due to malfunction of the 7th cranial nerve (facial nerve). This nerve moves the facial muscles, stimulates the salivary and tear glands, enables the front two thirds of the tongue to detect tastes, and controls a muscle involved in hearing.
Hemifacial spasm affects men and women but is more common among middle-aged and older women.
The spasms may be caused by
Hemifacial spasm is diagnosed when doctors see the spasms.
Magnetic resonance imaging (MRI) should be done to rule out tumors, other structural abnormalities, and multiple sclerosis, which can cause similar symptoms. Also, MRI can usually detect the abnormal loop of artery pressing against the nerve.
Botulinum toxin is the drug of choice for hemifacial spasm. It is injected into the affected muscles. The same drugs used to treat trigeminal neuralgia—carbamazepine, gabapentin, phenytoin, baclofen, and tricyclic antidepressants (see Table: Drugs Used to Treat Depression)—may be tried but are usually not helpful.
If drug treatment is unsuccessful, surgery may be done to separate the abnormal artery from the nerve by placing a small sponge between them.